The involvement of the cell membrane in avian oncornavirus-induced transformation will be examined. Antisera prepared against avian oncornavirus-induced tumors will be used to immune precipitate iodinated surface proteins of avian oncornavirus transformed cells. Molecular separation will be by polyacrylamide gel electrophoresis and comparison will be made between these proteins precipitable from the transformed cell surface and those precipitable from in vitro translation of the transforming RNA genome. The expression of the avian oncornavirus envelope antigen in mammalian cells transformed by this virus will be quantitated by radioimmunoassay and the contribution of those antigens to transplantation antigens will be assessed in transplantation immunity experiments.